"App developers are withdrawing their products for sale from the US versions of Apple's App Store and Google's Android Market for fear of being sued by companies which own software patents - just as a Mumbai-based company has made a wide-ranging claim against Microsoft, Apple, Google, Yahoo and a number of other companies over Twitter-style feeds, for which it claims it has applied for a patent."

I agree it will be interesting to see some statistics on this especially graphed over time and correlated with patent judgements and new lawsuit launches.

In the end though it seems a rather logical and eventual result. If the legal liability is too much in the U.S. companies will eventually just drop the U.S. market for it's products. The current patent system (along with other legal costs such as frivolous lawsuits) just adds another cost of doing business in the U.S. The biggest problem is that cost is NOT predictable and has been shown it can be rather high. Considering the dropping revenues for most vendors due to the poor economic climate, I would not be surprised to see less and less vendors decide to market their products in the U.S. It's really not that hard to track, the formula is not very complex. Putting values in for the variables, now that is another thing entirely.